Production of steel



manta Mu.- as, 1944 wa PRODUCTION OF STEEL Marvin I. U117 Nlalara Falls, N. Y.

Sr'lal No. 395,312

No Drawing. Application as 2c, 1941,

' '5 Claims.

This invention relates to metallurgy and has for an object the, provision of certain improveinents in metallurgical methods or processes and products.- More particularly, the invention concarbon is converted to an oxide form which is gaseous and which passes out into the atmosphere.

of thejconverter It has been proposed also to subiect iron of templates the provision of certain improvements 6' the typewof blast furnace iron and cupola iron in methods or processes and products suitable for use in the production of steel. .A particular object of the invention is to provide an improved method or process for removing silicon and carbon from iron ofthe type of blasts furnace iron and cupola iron.

Iron used in the production of steel customarily is produced in furnaces of the type ofblast iumaces and cupola furnaces; Iron thus produced contains relatively large amounts of sill-l con and carbon which must be removed or reduced in amount iniorder to produce suitable steel products. Thus, for example, iron of the type of blast furnace iron and cupola iron may contain carbon in amount equal-to about two and one-halfto three and one-halt percent (2.5 to 3.5%)- by weight and silicon in amount equal with substantial 'ulliflcation of the effects of the to, about one to three and one-quarter percent (1.0 to 3.25%) by weight.

In the production of steel, iron of the type pro-- duced in blast furnaces and cupolas is treated v ultimately in steel making furnaces of the type 'of open hearth furnaces and electric furnaces capacity of the furnace for steel production is 3 limited byexcessive volumes of slag which must be produced in the removal or elimination of M relatively large amounts of silicon and carbon.

Therefore, in order to avoid limiting the capacitles oi the steel making furnaces for steel production, it has been proposed to subject the iron of the type of blast furnace iron and cupola iron to a preliminary treatment, prior to introduction into the steel making furnace, to efiect 'the I removal of substantial proportions of the silicon and carbon.

According to some present practices,prelim-' inary treatment of iron of the type ofblast furnace iron andcupola iron for silicon and carbon removal involves treatment ot-the iron in Bessemer converters in which silicon and carbon are oxidized by means of air blown through the metal in the molten state. Silicon thus is or:- idiaed to silica (Sim) which enters a slag layer to a preliminary treatment with. iron oxide to oxidize and remove silicon and carbon priorgto introduction of the iron into "the 'steel making furnaces. This proposed procedure has not been particularly successful because of the high melting point of the silica produced by oxidation and because of the high melting points of and consequent high viscosities of the slags produced. Slag thus produced is sticky and stringy and dimcult to separate from the metal. Consequently, substantial amounts of iron may be lost with the slag removed if complete separation of the slag from the metal is attempted, or substantial amounts of the slag are retainedvwith the metal and delive ed to the steel making furnace preliminary treatment if complete separation of the metal and slag is not attempted.

The'present invention provides a simple and oeflective method of removing silicon and carbon from ironof the type of blast furnace and cupola iron prior to introduction ?of the iron into steel making furnaces." The invention also provides improved products which may be employed advantageuosly for the removal of silicon andcar-l bon from iron or for the adjustment of silicon and carboncontents at any stage of production of iron and steel in which the iron or steel s molten. v According to the methodor process of the invention, iron of the type of blast furnace iron and cupola iron issubjected while molten to the action of a metallurgical product in the form of *a mixture of iron oxide and-a compound'containingan'alkali metal'oxide as aconstituent.

Any suitable form of iron oxide may be em'- ployed. Thus, for example, iron oxide may be mployed in the form of ferric oxide (FezO'a) or in theform of magnetic iron oxide (mill scale) (Fe'soi). Compounds containing alkali metal oxide should be of the type in which the alkali metal oxide becomes available for combination with silica produced by oxidation of silicon to form alkali metal silicate under theinfiuence of v the hct molten metal and under the conditions of use of the compound. Suitable compounds containing available alkali metal oxide include sodium nitrate, sodium silicate, sodium carbon.

on the surface of the bath of molten metal and so ate and sodium bicarbonate. Sodium silicate preferably is employed in the form of the meta-- silicate (NazO-SiOz). I

Metallurgical products of the invention comprise iron oxide and one or more compounds containing available alkali metal oxide. Lime (090) or fluorspar (calcium'fluoride CaFz) or both may be included in the products. Products containing sodium nitrate may include, also, some silicon, in the form of ferrosilicon for example. l The products'of the invention may be employed in any suitable physical forms. Preferably, the components of the products are em-' In the preferred products in the invention,

the components preferably are in the form ,of particles suiiiciently small in size to pass a 100- mesh screen. The-mixtures of components of the products of the invention preferably are In the process of the invention. the iron oxide of the metallurgical product employed functions as a source-of owgen for oxidizing the silicon and carbon. When sodium nitrate is included in the metallurgical product employed, it func ployed. when sodiinn silicate (Nafiloa) or sodium carbonate is included as a component of the metallurgical product employed, it functions as a source of sodium oxide for combining with silica produced by oxidation of the silicon. .Lime may be incorporated in a metallurgical product of the invention for the purpose of combining with silica to produce calcium silicate, and

fluorspar may be included forthe purpose of .in-.

creasing the fluidity of slag produced. Com-- pounds such as sodium nitrate, sodium silicate v and sodium carbonate may function, also, as

formed by grinding together all of the com- .ponents to producea composite mass of particles largely, or entirely, small enoughxto pass a 100- mesh screen.

When the products of the invention'are produced and employed in the form of agglomerates or briquettes, the compound containing available alkali metal oxide preferably servesas the bonding agent. Agglomerates or briquettes may be formed by mixing the components intimately. shaping the mixture into agglomerates of suitable sizes and shapes under pressure, heating the shaped products to temperatures sufliciently high to melt the compound containing available alkali metal ing maybe facilitated by .wetting the intimate mixtures of components with an aqueous liquid in amountequal to about one to flvepercent oxide and cooling the heated products. Shaping of the products prior to heat- (lto5%) of the weightof the masstobeshaped.

Satisfactory agglomerates or'briquettes may be produced simply by shaping a wet mixture of the components and heating the shaped products to temperatures sufliciently high to drive. oil! all watenbut nothigh enough to melt the compound Any I suitable organic or inorganic bonding agent may be employed in forming agglomerates or brlquettes. Molasses water (an aqueous solution of containing available alkali metal oxide.

molasses); tar, pitch and asphalt are suitable bonding agents but their use is not particularly. desirable because their elimination requires consumption of oxidizing material.

. slag and metal. Lime or iiuorspar or both may.

Intimate mixing of the components promotes e'il'ective oxidation of the silicon and carbon of molten iro and eifeetive removal from the metal of the silica produced by oxidation by placing at the points of oxidation of silicon and production of silica alkali metal oxide available bonding agents for'the components of the mixtures when theproducts are employed in the form of agglomerates or briquettes.

The amount of any product of the invention which may be employedin carrying out a process ofthe invention and the relative proportions of various components employed in forming. that product will be determined, within certain limits, by the results sought to be accomplished. Generally, in carrying out a process of' the inventlon, a particular-product will be employed in amount suilicient to provide iron oxide or iron oxide and sodium nitrate containing available oxygen sufficient to accomplish the desired degree. of oxidation and removal of silicon and carbon. One or more compounds containing available alkali metal oxide, such as sodium nitrate, sodium silicate and. sodium carbonate will be unployed in amount suflicient to eflect the production of a low-melting point slag which will be suiiicientlyfluid at the temperature of the operation to facilitate clean separation'of the be included for the purpose of modifying the characteristics ofthe slag, and iron oxide may be employed in large or small excess for the same purpose. When the iron is relatively cold, additional heatmay be gipplied-to raise its temperaby in the product employed d and in amount at'least sufllcient to oxidize the silicon.

The method or. process of the invention m y be utilized,'if desired, to permit elimination of converters for removal-of silicon and carbon in those plants provided with converters and to would be introduced directly into the steel fur- -nace, the invention provides for an increase of as much as twenty percent (20%) in the steel making capacity of the furnace.

The metallurgical products of the invention assesses a 3'- may be brought into contact with the molten iron from which silicon and carbon is to beused in any suitable manner, as, for xample, by placing the products on the surfaces oi moltenbaths oi the iron or by pouring the molten iron into contact with the products in a ladle. In the preferred process or the invention. the metallurgical product to be employed is placed in a ladle and the molten iron is poured into the ladle and into contact with the product therein. This procedure produces effective contact and mixing of the molten iron with the product.

In carrying out a process in accordance with the invention, the molten iron preferably is employed at a temperature in the range 2500" F. to 3200 F. The composition of the metallurgical product employed is-adjusted to provide a fluid slag at the temperature orthe molten iron under going treatment.

The iollowing examples illustrate the process of the invention employing products oi the invention:

' Ekrample I Aproduct oi the invention was formed by I grinding together 35.6 pounds of mill scale (F8304) and 14.5 pounds of sodium nitrate to form an intimate mixture or particles small enough to pass, a l00-mesh screen. Theresulting mixture was shaped into the form of briquettes under pressure and heated to a temperature above the melting point but below the decom-" Example 11 Similar results were obtained when a similai. quantity 01 iron oi the same composition and temperature was poured into a-ladle containing briquettes comprising an intimate mixture of mill scale (F8304) and sodium carbonate and containing 64 pounds of mill scale and 12 pounds of sodium carbonate. The briquettes. were formed by grinding together the mill scale and sodium carbonate to form a mass or particles small enough to pass a loo-mesh screen, wetting the mass with water, shaping the 'wet ,mass under pressure and heating the shaped products to a temperature slightly'higher than the melting temperature of sodium carbonate.

I claim: I

1. The method of treating iron containing not less than about two and one-half percent of carbon and one percent of elemental silicon to remove silicon and carbon contained therein which comprises subjecting the iron while molten.

to the action of a mixture of materials comprising iron oxide, calcium oxide and sodium silicate. v 2. The method of treating ironcontaining not less than about two and one-half percent of carbon and. one percent of elemental silicon to remove elemental silicon and carbon contained therein which comprises subjecting the iron while molten to the action of a mixture or ma- .terials comprising iron oxide, elemental silicon-- containing material and sodium nitrate 3. The method or treating iron containing not less than about two and one-half percent of carbon and one percent of elemental silicon to remove elemental silicon and carbon contained. therein which comprises subjecting the iron while molten to the action of a mixture of materials comprising iron ol'dde, elemental siliconcontaining material, calcium oxide and sodium nitrate. i

' 4. A metallurgical product suitable for use in the treatment of molten iron containing not less than about two and one-half percent of carbon and one percent of elemental siliconior the removal or silicon and carbon cont ned therein, comprising particles of iron oxide and particles of silicon-containing material intimately asso-i ciated with and bonded together bymeans of sodium nitrate, the silicon oi the silicon containing material and the sodium nitrate being present in amounts and proportions suchas to be capable of reactingexothermically upon contacto'r the product with the-molten iron. and the silicon being present in amount not sub-- stantially in excess of that required for reaction with the sodium nitrate. 5. A metallurgical. product suitable for usein the treatment of molten iron containing not less than about two and one-half percent of carbon and one percent. of elemental silicon for the removal of silicon and carbon contained therein, consisting 01 particles of finely divided iron .oxide, finely divided calcium oxide and calcium fluoride intimately associated withand bonded together by means of one or more compounds of the group consisting 01! sodium nitrate, sodium silicate and sodium carbonate;

MARVIN J. UDY. 

